For diabetes treatment, the concentration of glucose contained in blood of a patient (hereinafter referred to as “blood glucose level”) need be maintained in a normal range, and the management of the blood glucose level by the patient himself or herself is an important treatment. Particularly, for the treatment of insulin-dependent diabetes, the patient needs to inject insulin by himself or herself to maintain the blood glucose level in a normal range, so that the measurement of the blood glucose level is essential for the patient.
Portable blood glucose level measuring instruments which can be used by the patient himself or herself is already commercially available, an example of which is disclosed in JP-A-4-357452. Generally, a blood glucose level measuring instrument comprises an instrument body, and a disposable sensor (test piece) for use as mounted to the main body. The sensor is provided with an enzyme electrode including an electrode portion and a reacting portion contacting the electrode portion. When a predetermined portion of the sensor is brought into contact with blood as an analyte, part of the blood is introduced into the reacting portion by capillary action, causing an enzyme reaction or an electrochemical reaction. As a result, an anode current is generated at the electrode portion contacting the reacting portion. The anode current is converted to a blood glucose level at an arithmetic circuit provided in the main body and the computation result is displayed at the display portion.
When such a sensor having an enzyme electrode, or a so-called biosensor is exposed to the air for a long period of time, the reagent contained in the reacting portion is deteriorated due to its absorption of water in the air. In such a case, accurate measurement results cannot be obtained. Therefore, this kind of sensor is supplied to the patient in a hermetically sealed state by wrapping the sensor with aluminum laminated film for example. In this case, for measuring the blood glucose level, the patient needs to first break the laminated film by hand and then take out the sensor from the laminated film wrappings for mounting to the measuring instrument. These steps need be performed properly without touching the enzyme electrode portion or the analyte-contacting portion, which gives psychological stress to the patient. This is rather serious for children, the elderly, adults who recognize not to be clever with their hands, or visually-defected patients. Since this kind of measuring instrument is usually designed to perform proper measurement with as small amount of analyte as possible, there is a tendency to reduce the size of a sensor. Accordingly, the proper handling of a sensor becomes increasingly difficult for the patient.
As a manner of hermetically sealing the sensors, a plurality of sensors may be collectively sealed in a can provided with a lid for example, instead of individually wrapping each sensor with a laminated film as described above. According to this arrangement, for measuring the blood sugar level, the patient needs to open the lid of the can to take out one sensor for mounting to the measuring instrument. This causes a problem that all the sensors in the can are exposed to the air every time the lid is opened. Further, this arrangement does not considerably facilitate the handling of the sensors as compared with the manner of wrapping the sensors with laminate films. Thus, the handling of the sensors become difficult as the sensors become smaller in size.
JP-A-6-308115 discloses another manner of hermetically sealing the sensors, which utilizes a cartridge. The cartridge includes a plurality of chambers arranged in a row, each of which accommodates a sensor. Specifically, each chamber of the cartridge has a cylindrical configuration which is open at opposite ends thereof. The sensor cartridge is mounted to a predetermined sensor feeder provided with a projecting bar. By inserting the projecting bar into each of the chambers through one end toward the other end thereof, the sensor is pushed out from the chamber through the other end.
With this arrangement, the handling of the sensors is easier than in the above-described arrangements, because the user, or the patient need not manually peel off the sealing member at each chamber of the sensor cartridge. However, it still has the following problems.
Firstly, since the sensor pushed by the projecting bar needs to break through the sealing member sealing the end of the chamber, the materials for the sensors are limited to certain kinds in view of the rigidity. This may hinder the size reduction and thickness reduction of the sensors.
Secondly, the manufacturing of the sensor cartridge is troublesome, because it is required to insert sensors in respective chambers and to separately seal opposite ends of each chamber with a sealing member.